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New Australian research has resolved an ongoing debate regarding the timing of a major tectonic plate collision in the South Pacific region, the effects of which we're still experiencing.

The research, published in the latest edition of Nature, reveals that the Australian plate collided with the Ontong Java Plateau (OJP), the world's largest and thickest oceanic plateau, between 23 and 26 million years ago.

Prior to this research most scientists believed the collision took place in the early Miocene period - between 20 to 30 million years ago - although some argued it was recent as four million years ago.

Doctor Kurt Knesel and colleagues from the University of Queensland calculated the date of the collision using information found in volcanoes in eastern Australia.

"This event was so important because it triggered a change in the plate motions and boundaries in the Pacific ... and led to the current set of plate motions which we're still experiencing," Knesel said.

The timing of the OJP's collision with the Australian plate has been controversial because scientists were unable to establish how or when the collision occurred as they couldn't access the OJP, which is buried under several kilometres of ocean sediment.

Land-based research

For this study Knesel and PhD student Ben Cohen gathered their information from land-based volcanoes that run along eastern Australia from central Queensland through to southern Victoria.

The researchers were able to track the Australian plate's movement northwards from Antarctica by noting the age progression of the volcanoes, the further south they went the younger the volcanoes were.

Knesel says the researchers used high resolution dating techniques to determine the volcanoes' ages, which allowed them to pinpoint when the Australian plate ran into the OJP by identifying a period of slower volcanic activity.

"What we saw in that boundary between northern New South Wales and southern Queensland - where the volcanoes were around 25 million years old - the age migration pattern slowed down for a couple of million year period, between 26 and 23 million years ago," he says.

"It slowed down by almost a third, this suggests lower plate motion."

Ocean findings

The researchers then looked for volcanic remains on the seafloor that corresponded in time and place to the OJP collision to corroborate their findings.

Knesel says they found tracks of submarine volcanoes were similar to those found on land.

"There's a bend to the east in the seamount chains and it fits perfectly with the time that we see the plates slow down - so both those pieces of evidence really point to the collisional event being the Ontong Java Plateau."